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JavaScript JavaScript Array Iteration Methods Array Manipulation Remove Array Items with filter()

karan Badhwar
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karan Badhwar
Web Development Techdegree Graduate 18,135 Points
Posted by karan Badhwar
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karan Badhwar
Web Development Techdegree Graduate 18,135 Points

How filter() or setTimeout() methods invoke functions without parenthesis

As we just pass in the name of the variable holding the function, but how does they invoke it, generally we pass that via parenthesis, but how this happens?

And how to tell where do I need to add Parenthesis and where not?

1 Answer

Steven Parker
Steven Parker
229,744 Points
Steven Parker
Steven Parker
229,744 Points

A "callback" argument is a reference to a function. You are not actually calling the function when you pass the reference.

At a later time, the system will invoke the function by using parentheses. This happens in internal code that you don't actually see.

So, you use parentheses when you want to invoke the function yourself and pass along whatever that function returns. But you do not use parentheses when you want to pass a reference to the function itself.

Steven Parker
Steven Parker
229,744 Points
Steven Parker
Steven Parker
229,744 Points

I've been a software developer for a very long time. Lots of practice!